Lithium ion battery

Abstract

In a lithium ion battery, one or more chelating agents may be attached to a microporous polymer separator for placement between a negative electrode and a positive electrode or to a polymer binder material used to construct the negative electrode, the positive electrode, or both. The chelating agents may comprise, for example, at least one of a crown ether, a crown ether, a podand, a lariat ether, a calixarene, a calixcrown, or mixtures thereof. The chelating agents can help improve the useful life of the lithium ion battery by complexing with unwanted metal cations that may become present in the battery's electrolyte solution while, at the same time, not significantly interfering with the movement of lithium ions between the negative and positive electrodes.

What is claimed is: 
     
       1. A lithium ion battery, comprising:
 a positive electrode; 
 a negative electrode; 
 a microporous polymer separator soaked in an electrolyte solution, the microporous polymer separator disposed between the positive electrode and the negative electrode; and 
 a chelating agent chemically attached to the microporous polymer separator, a binder material of the negative electrode, or a binder material of the positive electrode, and wherein the one or more chelating agents complex with transition metal cations but complex less strongly with lithium ions so that the movement of lithium ions between the negative and positive electrodes is not substantially affected; 
 wherein the chelating agent is selected from the group consisting of a crown ether, a cryptand, a podand, a lariat ether, a calixarene, a calixcrown, or a mixture of two or more of these chelating agents. 
 
     
     
       2. The lithium ion battery as defined in  claim 1  wherein the microporous polymer separator, the binder material of the negative electrode, or the binder material of the positive electrode is a polymer and wherein the crown ether attached to the polymer is a cyclic ether, and wherein oxygen atoms of the cyclic ether are to complex with the transition metal cations. 
     
     
       3. The lithium ion battery as defined in  claim 1  wherein the chelating agent is selected from the group consisting of 15-crown-5, 15-crown-5 with at least one of its oxygen atoms exchanged for a nitrogen atom, 18-crown-6, and 18-crown-6 with at least one of its oxygen atoms exchanged for a nitrogen atom, and wherein the chelating agent includes one of 2-hydroxymethyl, hydroxymethyl-benzo, or 2-aminobenzo attached thereto. 
     
     
       4. The lithium ion battery as defined in  claim 1  wherein the chelating agent is the cryptand and includes one of 2-hydroxymethyl, hydroxymethyl-benzo, or 2-aminobenzo attached thereto. 
     
     
       5. The lithium ion battery as defined in  claim 1  wherein the chelating agent is selected from the group consisting of: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
       and wherein the chelating agent includes one of 2-hydroxymethyl, hydroxymethyl-benzo, or 2-aminobenzo attached thereto. 
     
     
       6. The lithium ion battery as defined in  claim 1  wherein the chelating agent attached to the microporous polymer separator, the chelating agent attached to the binder material of the negative electrode, or the chelating agent attached to the binder material of the positive electrode is a crown ether substituted olefin that is cross-linked with a cross-linking agent of divinylbenzene with azobisisobutyronitrile. 
     
     
       7. The lithium ion battery as defined in  claim 1  wherein the microporous polymer separator is a polyolefin with a formula: 
       
         
           
           
               
               
           
         
       
       wherein n and x are integers, wherein X is I, Br, or Cl, and wherein the chelating agent includes a group that nucleophilically displaces X to attach the chelating agent to the polyolefin, the group being selected from the group consisting of 2-hydroxymethyl, hydroxymethyl-benzo, or 2-aminobenzo. 
     
     
       8. The lithium ion battery as defined in  claim 1  wherein a polymer binder material of the negative electrode or a polymer binder material of the positive electrode include at least one of polyvinylidene fluoride, an ethylene polypropylene diene monomer rubber, or carboxymethyl cellulose. 
     
     
       9. A method, comprising:
 forming a crown ether or a cryptand, the crown ether or the cryptand having one of an OH group or an NH group attached thereto; and 
 replacing a halide ion attached to a polymer with the crown ether or the cryptand, thereby forming a polymer material having a pendant crown ether or a pendant cryptand. 
 
     
     
       10. The method as defined in  claim 9  wherein the OH group is selected from the group consisting of 2-hydroxymethyl and hydroxymethyl-benzo, or wherein the NH group is 2-aminobenzo. 
     
     
       11. The method as defined in  claim 9  wherein the polymer is a polyolefin with a formula: 
       
         
           
           
               
               
           
         
       
       wherein n and x are integers, and wherein X is I, Br, or Cl. 
     
     
       12. The method as defined in  claim 9  wherein the chelating agent is selected from the group consisting of 15-crown-5, 15-crown-5 with at least one of its oxygen atoms exchanged for a nitrogen atom, 18-crown-6, and 18-crown-6 with at least one of its oxygen atoms exchanged for a nitrogen atom, and wherein the OH group is selected from the group consisting of 2-hydroxymethyl and hydroxymethyl-benzo, or the NH group is 2-aminobenzo. 
     
     
       13. The method as defined in  claim 9  wherein the cryptand includes one of 2-hydroxymethyl, hydroxymethyl-benzo, or 2-aminobenzo attached thereto. 
     
     
       14. The method as defined in  claim 9  wherein the crown ether is selected from the group consisting of: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
       and wherein crown ether includes one of 2-hydroxymethyl, hydroxymethyl-benzo, or 2-aminobenzo attached thereto.